Apparatus for reducing sheath currents



F. J. \NHITE Ami 1, 193a,

APPARATUS FOR REDUCING SHEATH CURRENTS Original Filed April 8, 1927 hetented EEAHGL'S bi th TEE, @E BEQQIZLYK', NEW WEEK, nssre'nonl T6 TEE OEQEITE GQEEZPAEGX, @F PASSAIC, NEW JERSEY, A. CQRLQRATIQN 6F NEW JERSEY APPARATUS FOE JEEB'UCIN& SEErhTE @riglnel amelioration filed April it, 19b7, Serial Ito. 181,918. Divided and this application filed February 2'58 H928. Serial lilo. 25?,tlth

The present invention reletes to an imrovernent in electric apparatus and particuurly to epparatus for use in connection with conductor cables for carrying alternating or s pulsating currents, and has for one of its objects the provision of an apparatus for reducing the currents induced in the sheath covering the cable, these currents being reterred to hereinafter as sheath currents.

It is well mown that the passage of an alternuting or pulsating current through a single conductor cable or the unbalsncing of alternetin cable in uces en electromotive force in the to ceble sheath or other metallic cover with which the cable may be provided, which if this sheath or other metallic cover is not connected to ground or to other conducting paths may cause a dangerous diderence of potential so between the metallic cover end Mjecent structures. lit is e. further object of my invention, therefore, to reduce or, if desired, to neutralize this action. On the other bend it the metallic cover is electrically connected with other conducting paths so as to form a complete circuit a current is set up. This socslled sheath current in addition to the losses in transmission it causes has on appreciable efiect on the heating of the cable and hence reduces the permissible current in the conductor,

The present invention has special reference tojunction or joint boxes through which the adjacent ends of two lengths oi conductor cable are joined together, and in which structures the dificulties above reierred to are encountered. The present application is e division of my co-pending application No. 181,916, filed April 8, 1927, in which application my invention is claimed with relation to the reduction of sheeth currents in a cable without special reference to junction boxes.

The present epplicetion will be confined to eppsretus for use in connection with joint or junction boxes.

"in the drawings, Fig. l shows on embodiment of my invention in elevation; and

Fi 2 is on end view of the megnetizoble mom er of Fig. 1.

Referring to the l 2 desigcurrents in a multiple conductor box or in any event in inductive relation to the conductor or conductors of the cable 1 apply a member 8 of magnetizeble material, insulation 9 being interposed between this member and the metal of the section 6 of the box. This member 8, as illustrated, is composed of laminations l0 and 11 erran ed in overlapping position and held in'ad usted position by bolts 12. 'lhe laminated structure is so assembled as to provide an air gap 18, the width of which can be adjusted rendily by merely changing the relative ositions of lsrninations l0 and 11, to vary t e reluctance of the magnetic circuit oi the structure, or the same efiect, electrically, can be obtained by entirely removing some of the laminations. The construction of the member 8 as just described may be varied it desired by substituting solid rings for the laminations 10 end 11, it being understood oi course that l would still have a built up laminated structure, and that the necessary edjustments could be efiected by varying the number of rings or snnuli em loye A conductor M has one en thereof con-= nected to the metallic end plate 5 oi the junction box to which the cable length 2 is connected or to the sheath of cable length 2 while its other end is connected to the remote end or the intermediate portion 6 of the box. Likewise e conductor 15 has one end connected to the metallic end plate l oi the joint or junction box or to the sheath of cable length 1. The other end of this conductor is connected to the remote end oi the inter mediate portion b of the box. It will be ob-= vious the two eonduo= ice tors ll and will in conjunction with the intermediate member 6 of the joint box function as a one turn neutralizing coil for the core 8, and that the electromotive force induced in the sheath of the cable length 1 and lengths l and 2, respectively. In such case it is evident'that the end of the conductor 14, now connected to the member 5, must be connected to the sheath of cable length 2, while the end of conductor 15, now connected to member l, must be'connected to the sheath of cable length l.

It will be seen, therefore, that l have provided an apparatus capable of installation at the joint or junction boxes by which two adjacent cable lengths are attached to each other whereby so-called sheath currents are reduced or, if desired, may be completely neutralized, it being understood as above explained that the member 8 may be adjusted as desired thereby eliminating or reducing to a degree where no longer detrimental the setting up of dangerous potentials in the cable covering.

It is to be understood furthermore that while I have illustrated and described reducing or neutralizing means in whichjan annulus of magnetizable laminated material is employed, my neutralizing or reducing means may take other terms, if desired, provided or course the same is magnetizable by the current or currents flowing in the conductor or conductors of the cable.

It is to be further understood, as above pointed out, that my invention is applicable to joint boxes connecting cable lengths of either the single or multiple conductor type,

and that the appended claims are to be so interpreted.

l/Vhat I claim is 1. In combination a junction or joint box for connecting the conductors of two lengths of an electric cable,- a section of said junction or joint box being insulated from adjacent sections of the junction or joint box and from the adjacent sheath of said lengths of electric cable, a core of laminated magnetizable material disposed about the insulated portion of said box and in inductive relation to the cable conductor therein, each end of said insulated section being connected by a conductor to the remote cable sheath.

2. In combination a junction or joint box for connecting the conductors of two lengths of an electric cable, a section of said junction or joint box being insulated from adjacent, sheaths of said lengths of electric cable,

an adjustable core oi laminated magnetizable material disposed in inductive relation to the cable conductor within the insulated section of the joint box, each end of said insulated section of the joint box being connected by a conductor to the remote cable sheath.

3. In combination a joint box for connect ing the conductors of two lengths of an electric cable, a section of said joint box being insulated from adjacent sections and from adjacent sheaths of said lengths of electric cable, a core adjustable as to the reluctance of its magnetic circuit positioned in inductive relation to the conductor of said lengths of cable within the insulated section of the junction box, and conductors connecting said insulated section of the junction box and the adjacent cable sheaths to provide electrically, in cooperation with the insulated section of the junction box, a coil for the said core.

4. In combination a junction or joint box composed of two sections and an intermediate section insulated from each other, a core of magnetizable material about the intermediate section of the box and conductors connecting the intermediate section of the joint box to the end sections and providing electrically with the intermediate section a coil 'for the said core.

5. In a junction or joint box the combination of two metallic end sections, an intermediate section of non-magnetizable mate-v rial insulated therefrom, a magnetizable core tion, said core being provided with an adjustable air gap, and conductors connecting the intermediate section and one end. section and the intermediate section and the other end section in opposition, said intermediate section and said conductors cooperating to provide electrically a coil for said core.

6. In combination, a joint box, cable lengths united through said joint box, a member of magnetizable' material disposed about the exterior of the box and in inductive relation to the conductors of the cable within-the box, sheaths for said cables outside said box and insulated therefrom, a conductor connecting the oint box and one of said sheaths, another con uctor connecting the box and another of said sheaths in opposition. to the first-mentioned connection to oppose the electrometive force induced in the sheaths of the cable lid 

